This invention relates to an auxiliary propelling equipment mounting arrangement for sail boat or other water craft, and more particularly to an improved sealing structure and leakage detection device therefor.
Many forms of sail boats employ an auxiliary propelling unit such as an engine and drive unit that may be mounted so as to extend through a hole in the hull. As is well known, it is desirable to remove such propelling unit when not in use so as to avoid unnecessary drag from the drive unit. It is desirable to provide an effective seal between the auxiliary propelling unit and the hull when the propelling unit is in place to prevent leakage. Such a seal should be highly effective and yet must permit ease of insertion and removal of the auxiliary power unit. In one form of prior art arrangement the seal is provided by an O-ring-like member that is carried by the auxiliary propelling unit and which is adapted to sealingly engage a portion of the hull that defines the opening when the power unit is in place. Such arrangements have a number of disadvantages. In the first instance, considerable insertion force is required to insure effectiveness of the seal. Furthermore, since the seal is carried by the auxiliary power unit, it is prone to damage particularly upon successive insertions and removals; thus, rendering the seal ineffective. This type of seal also does not permit any wide degree of movement and, thus, affords no vibration damping, which is undesirable with this type of installation.
It is, therefore, a principal object of this invention to provide an improved sealing arrangement for an auxiliary power unit of a watercraft.
It is a further object of the invention to provide an auxiliary power unit seal that permits ease of installation or removal of the power unit, while minimizing the likelihood of damage to the seal.
It is yet a further object of this invention to provide a sealing arrangement for an auxiliary power unit which permits a wide degree of relative movement generated by vibrations while at the same time maintaining an effective seal.
In conjunction with the use of seals that permit large degree of relative movement so as to minimize the transmission of vibrations to the hull, it is essential that an arrangement be incorporated which will minimize the likelihood of damage under large magnitude movements such as may be encountered if a submerged object is struck by the power unit. It is desirable to avoid direct solid contact between the power unit and the hull under such conditions. If the power unit is permitted to directly strike the hull, damage might well occur.
It is, therefore, a yet further object of this invention to provide a resilient seal for an auxiliary marine power unit that incorporates a resilient damping device for large magnitude movements.
In order to provide an effective seal around the auxiliary power unit of a water craft, it has been proposed to provide a double seal arrangement consisting of a lower seal and an upper seal that define a cavity of space between the two seals. Such a double sealing arrangement provides additional sealing protection in the event one of the seals deteriorates or becomes damaged. If, on the other hand, the lower seal becomes damages, the leakage past it may not be noticed and the seal may not be repaired in time. It has, therefore, been proposed to provide some form of sensing device which senses the presence of water between the two seals to provide an indication that one of the seals has failed. However, it is important that the sensing device by mounted in such a way that it will not interfere with removal and insertion of the auxiliary power unit. Furthermore, the arrangement should insure that the sensing unit will not be damaged upon power unit replacement or removal, or that the seal itself will be damaged on such removals or insertions. It has been proposed to mount the sensing unit directly upon the seal. If this is done, it must be insured that the connection of the sensing unit to the seal does not itself leak. To avoid this problem, it has been proposed to form the sensing unit as an integral part of the seal. However, this also has a disadvantage. If either the seal of the sensing unit becomes damaged, it is necessary to replace both units.
It is therefore, a further object of this invention to provide a improved leakage sensing arrangement for the seal of a marine auxiliary propullsion unit.